configure: Fix detection of libdir in ldconfig configuration

Ever since commit b4b5e9ce4d the
detection of libdir in the ldconfig configuration has been broken,
resulting in RPATH being set when not needed and not wanted.

The cause was a change from an IFS setting of:

	IFS="$(printf '\n\t')"

to a new setting of:

	IFS="$(printf '\n')"

That looks desirable since we want to split the output of ldconfig
based on newlines, (and not split on any filename that might have an
embedded tab in it). The subtle bug in the above is that the shell
trims any trailing newlines when performing command substitution so
the final statement above was equivalent to:

	IFS=''

which prevented any splitting of the ldconfig output at all.

Fix this by avoiding command substitution and just using a literal
newline in the source file for setting this variable.

configure

@@ -355,17 +355,30 @@ elif [ $uname = "Linux" ] ; then
     printf "Linux\n"
     platform=LINUX
     linker_resolves_library_dependencies=1
+
+    printf "Checking for $libdir_expanded in ldconfig... "
     ldconfig_paths=$(/sbin/ldconfig -N -X -v 2>/dev/null | sed -n -e 's,^\(/.*\):\( (.*)\)\?$,\1,p')
     # Separate ldconfig_paths only on newline (not on any potential
-    # embedded space characters in any filenames).
+    # embedded space characters in any filenames). Note, we use a
+    # literal newline in the source here rather than something like:
+    #
+    #	IFS=$(printf '\n')
+    #
+    # because the shell's command substitution deletes any trailing newlines.
     OLD_IFS=$IFS
-    IFS="$(printf '\n')"
+    IFS="
+"
     for path in $ldconfig_paths; do
 	if [ "$path" = "$libdir_expanded" ]; then
 	    libdir_in_ldconfig=1
 	fi
     done
     IFS=$OLD_IFS
+    if [ "$libdir_in_ldconfig" = '0' ]; then
+	printf "No (will set RPATH)\n"
+    else
+	printf "Yes\n"
+    fi
 else
     printf "Unknown.\n"
     cat <<EOF